The present invention relates to improvements in torque transmitting apparatus. More particularly, the invention relates to improvements in torque transmitting apparatus which can be utilized with advantage in the power trains between the engines and the wheels of motor vehicles. Still more particularly, the invention relates to improvements in reversible torque transmitting apparatus which can be utilized between the output elements of engines and the differentials of motor vehicles.
It is already known to utilize in motor vehicles reversible torque transmitting apparatus which employ planetary transmissions of the type having a sun gear or wheel, an internal gear or wheel, a rotary planet wheel carrier, and one or more planet pinions or wheels rotatably mounted on the carrier and mating with the sun wheel as well as with the internal gear. Reference may be had, for example, to German Pat. No. 34 24 856 C 2 which discloses a start-up element serving to receive torque from the engine of a motor vehicle and to transmit torque to an input element of a reversible torque transmitting apparatus which employs a twin planetary transmission. The transmission is blocked while the vehicle is being driven in the forward direction. If the vehicle is to be driven rearwardly, the internal wheel of the transmission is braked to prevent rotation relative to the transmission housing, and the transmission then receives or transmits torque by way of its sun wheel. A drawback of the patented apparatus is that, when the vehicle is driven in a forward direction, the force which is to cause a clutch of the patented apparatus to block the planetary transmission, by connecting the planet wheel with the sun wheel, must be applied to a rotating shaft. This can be achieved by resorting, for example, to an antifriction ball or roller bearing or by resorting to a hydraulic rotary transmission. In either event, the patented apparatus operates with loss of power due to the development of drag torque. This results in a drop of the efficiency of the entire power train and contributes to higher fuel requirements of the engine of the motor vehicle. In addition, presently known reversible torque transmitting apparatus are rather bulky, expensive and prone to malfunction.